Video editing software and browsers generate temporary filenames to avoid overwriting existing data.
If you must open it, use a sandboxed media player like VLC Media Player rather than default system players. mjhyt678ytfvcds.mp4
To help me give you a more tailored write-up, could you tell me: did you find this file? mjhyt678ytfvcds.mp4
Verify where the file came from before attempting to play it. mjhyt678ytfvcds.mp4